Photonics Dictionary

light-emitting diode

An LED, or light emitting diode, is a semiconductor device that emits light when an electric current passes through it. LEDs are widely used in various applications due to their energy efficiency, compact size, and long operational life. The technology behind LEDs is based on the phenomenon of electroluminescence.

Key characteristics and features of LEDs include:

Electroluminescence: The process by which LEDs emit light is called electroluminescence. It involves the recombination of electrons and electron holes in a semiconductor material, resulting in the release of energy in the form of photons (light).

Semiconductor structure: The basic structure of an LED consists of a semiconductor material, which is typically a compound semiconductor like gallium arsenide (GaAs) or gallium phosphide (GaP). The semiconductor is doped with impurities to create regions with excess electrons (n-type) and regions with electron deficiencies or "holes" (p-type).

Energy band gap: Electroluminescence occurs when electrons in the conduction band of the semiconductor recombine with holes in the valence band, releasing energy in the form of photons. The energy band gap of the semiconductor determines the color of the emitted light.

Colors: LEDs are available in a variety of colors, including red, green, blue, and white. The choice of materials and the doping process influence the wavelength of the emitted light, determining the color.

Energy efficiency: LEDs are highly energy-efficient compared to traditional incandescent bulbs. They convert a higher percentage of electrical energy into light and generate less heat.

Long lifespan: LEDs have a long operational life, typically lasting tens of thousands of hours. This longevity is attributed to the absence of a filament or glass bulb, which can wear out or break in traditional light sources.

Instantaneous on/off: LEDs light up quickly when an electric current is applied, and they can be switched on and off rapidly without impacting their lifespan or performance. This characteristic is beneficial in applications like lighting and displays.

Compact size: LEDs are small and can be manufactured in various shapes and sizes, making them suitable for diverse applications, including indicator lights, displays, automotive lighting, and general illumination.

Directional emission: LEDs emit light in a specific direction, contributing to their efficiency in applications where focused or directional illumination is desired.

LEDs have become ubiquitous in everyday life, finding applications in various industries, including lighting, electronics, communications, signage, and more.

light-emitting diode

Presented by Dan Courtney, Three Rivers Community College

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